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I've looked around the website, but couldn't find an answer, so I'm posting this as a new item.

I'm just a guy who had a system installed. So, the answer to my question may seem obvious. But, I'm looking for one!!

There are 2 condensate lines coming out of the coil. My understanding is that one is the "regular" line, the other an "overflow" in case the "regular" one plugs up. Yhe "regular" one has a trap and runs to the outside of the house. The overflow comes out of the coil and does a 90 to point down to the cement garage floor.

My question : should I be feeling air blowing out of the end of each line? And, if air should be blowing out, how do you eliminate the whistle-like sound coming from the overflow line?

i have noticed when i install an evaperator that it comes with two mail threaded fittings with female glue fittings on the other end .one of the fittings has a smaller hole in it so not much air will blow out . i would try to use that fitting with the smaller hole as the secondary and of course put a trap on the primary line

I wouldn't lose any sleep over the air lost through the secondary drain line. Usually the secondary pan outlet doesn't have a full bore 3/4" opening as does the primary outlet, and it beats the alternative, which would be a flooded furnace interior and the possible damage to electronics. There should be no air coming out of the primary drain outlet if it is trapped and the trap is filled. However, some choose not to trap the primary on a positive side coil, and that works just as well if not better anyway.

There is nothing more frightful than ignorance in action....Mark Twain

I agree that with the setup you have air would be coming out both lines anytime the fan is on.
BUT you said that the primary drain exits the house well so is you heat and a/c that you are paying for
and i also agree that because its on the positive side of the system that it does not have to be trapped but who wants to try to cool their backyard with the current energy costs?

Like dash stated, the trap on the secondary will be useless because it will only have water in it if there is a problem.

There are items called "waterless traps" that eliminate this issue of wasting conditioned air to the outside. Also, a disconnect switch in leiu of a trap on the secondary drain will shut down the system if there is an overflow of condensate without having to run an open condensate drain.

I'v heard the suggestion that you can put mineral oil in the secondary trap, and it won't evaporate. It's non-toxic since you can use it as laxative. I figure if you can drink it it's okay in your condensate line.

The trap on the secondary drain becomes very important when the secondary drain becomes the primary drain. Of course when the secondary isn't being used the trap is useless as is the entire line. It's not necessary to keep the secondary line primed with mineral oil or anything else IMO. The first time the system shuts off the trap will become charged, if not before.

There is nothing more frightful than ignorance in action....Mark Twain